This invention relates to a passive safety harness for use in a motor vehicle.
It has been proposed to provide a so-called "passive" safety harness for use in a motor vehicle. Such a safety harness is fully automated in that, in response to a signal generated when a person is seated within the motor vehicle (for example, the signal may be generated in response to the door of the motor vehicle being closed) a mechanism is activated which places the various belt portions of the harness in position to restrain the person in the event that an accident arises. Similarly the mechanism can be activated (for example in response to opening of the door) to remove the safety harness from the person sitting in the motor vehicle.
One example of such a safety harness is disclosed in British Patent Specification 1366911.
In this safety harness part of the harness is formed by a lap belt which extends from an inertia reel to a carriage which is movable along a rail formed in the door of the vehicle. The carriage moves to one end of the rail when the harness is to be released and moves to the other end of the rail when the harness is to be closed in a position in which it retains a person within the vehicle. It is desired that the end of the safety belt which is attached to the carriage should remain in this latter position in the event that an accident arises, and thus means are provided in order to secure the carriage, and the end of the belt attached thereto, in the desired position. The particular arrangement used comprises a conventional safety belt buckle which may be mounted on the door of the vehicle and a conventional tongue, dimensioned to be received within the buckle, which is mounted on the carriage. When the carriage moves to its terminal position at the appropriate end of the rail the tongue is inserted into the buckle and thus, in the event that an accident arises, any force generated within the lap belt is transferred, through the carriage to the tongue and from the tongue to the buckle, so that the end of the lap belt connected to the carriage does not move in an undesirable manner. Means are provided to release the conventional safety belt buckle, in British Patent Specification 1366911, for example as the door is opened so that the carriage can then be moved along the rail, or withdrawing the tongue from the buckle. The carriage then moves to the other end of the rail.
The prior art arrangement suffers from two disadvantages.
The first disadvantage is that a conventional safety belt buckle is primarily designed to withstand a force applied thereto by a safety belt, the force being almost precisely aligned with the axis of the buckle. Since the buckle is designed to withstand a maximum force applied axially of the buckle, the buckle can only safely withstand a lesser force which is applied at an inclination to the buckle. If, as in the prior art, the buckle is restrained in a position in which the plane of the buckle is substantially parallel with the plane of the rail in the door, it will be appreciated that the buckle will not be aligned with the direction in which force will be applied to the buckle in an accident situation, since the belt portion attached to the carriage which is connected to the buckle extends substantially horizontally across the lap of the person wearing the harness.
A further disadvantage of the prior art is that if the safety buckle is connected to the door of the vehicle, then the force applied to the buckle during an accident situation is transferred to the door, meaning that the door must be made to be very strong if the door is able to withstand these forces, or further means must be provided to secure part of the door or an element connected to the buckle to the chassis of the vehicle to provide a sufficient degree of strength.